The manufacturing of integrated circuits or IC's has become a huge industry in recent years. The industry is expected to grow in the same manner in the foreseeable future. At the heart of the industry is the capacity to integrate a highly complex integrated circuit chip in an integrated circuit assembly for placement on a circuit board for interaction with other circuits in an electronic device.
The IC assembly will typically include the IC chip and some type of mounting structure to support the chip. A lead frame is typically secured to the mounting structure. The individual electrical conductors in the lead frame extend from the chip to form pins for electrical contact with other components in a circuit as well as for mounting the IC. The individual conductors in the lead frame are connected to predetermined areas on the chip with lead wires typically soldered therebetween.
A number of integrated circuit designs include a ceramic base for mounting the lead frame and chip. The base includes a thin layer of glass. The base with a lead frame positioned thereon is heated to render the glass layer liquidous. The weight of the lead frame on the base causes it to become embedded in the glass layer. Upon cooling, the lead frame is hermetically sealed within the glass layer on the base.
The integrated circuit chip may then be positioned on the base and electronically interconnected to the lead frame. A ceramic cover may then be applied over the lead frame and chip. The cover also includes a glass layer which may be heated to sandwich the lead frame and chip between the base and cover.
This particular integrated circuit design has significant value in military applications. The sandwiched design protects the sensitive components of the IC from shock and moisture and thereby increases reliability. The design has also been found to be very advantageous for use in relatively high temperature environments.
An important factor in the manufacture of integrated circuits is the ability and capacity to manufacture a large number of integrated circuits to reduce the per capita cost to a competitive level. It is not unusual for the particular integrated circuit design discussed above to have a production run of 800,000 to a 1,000,000 IC's produced each week by a single company. Therefore, any apparatus or method for reducing the manufacturing costs is important to the industry.
In the past, manual labor has been used to mount the base and lead frame in a metal frame structure referred to as a "boat" in the industry. The usual boat is designed to position a large number of bases and lead frames in a predetermined position for entry into an oven to embed the lead frame in the glass layer of the base. The boats include vertical walls to act as guides to position the base and lead frame. One such boat is manufactured and sold by Damco labs of Redwood City, Calif.
To achieve the necessary manufacturing tolerances of between 10 and 15 thousandths of an inch, manual labor has been used extensively to individually position and align the bases and lead frames within the boats.
The close tolerances required have made automation of the process impractical. In addition, the open framework nature of the prior known boats have often permitted either bases or lead frames to fall through the structure defining the positioning walls. These factors have reduced efficiency in manufacture.
Therefore, a need has been shown to increase the ease of IC manufacture by swiftly and accurately positioning a base and lead frame for entry into an oven to embed the lead frame. In addition, a need has arisen to automate the positioning of a lead frame and base for embedding, thereby reducing costs and increasing output.